Short answer. Yes. The rule's bar has an express exception: claims not filed in time may still be set forth as counterclaims in any action the executor or administrator brings against the claimant. Being sued by the estate reopens the door your missed deadline closed.
What the law says
otherwise they are barred forever, except that they may be set forth as counterclaims in any action that the executor or administrator may bring against the claimants
Rule 86, Section 5 — Claims which must be filed under the notice. Read the full provision →
The bar is not as absolute as it first reads
The rule states that unfiled claims are barred forever, which sounds like the end of the matter. The same sentence then carves out an exception, and it is the exception that matters to anyone in your position. A claim that can no longer be pressed against the estate on its own may still be raised as a counterclaim in an action the executor or administrator brings against the claimant. The bar stops you from attacking; it does not strip you of your answer when the estate comes after you.
Why the exception is fair rather than a loophole
The filing period exists so an estate can be wound up without unknown obligations surfacing indefinitely. That rationale runs out once the estate chooses to sue. Having elected to litigate against you, the estate has reopened the account between you, and it would be one-sided to let it collect in full while your own claim on the same relationship stays sealed off. The exception keeps the period doing its real job — protecting orderly settlement — without turning it into a weapon.
It depends on the estate suing you
Read the trigger carefully, because it is narrow. The exception applies to an action that the executor or administrator may bring against the claimants. It is not a general revival of a lapsed claim, and it does not let you start proceedings of your own. If the estate never sues, the exception never opens. That is also why this is not a reason to treat the original filing period casually: the safe course is always to file within the time limited in the notice, and to treat the counterclaim route as a rescue, not a plan.
Raise it in your answer, not later
The rule speaks of the claim being set forth in the action, so this is something to put forward in the pleading rather than to keep in reserve. The same provision also deals with mutual claims being set off against each other where the administrator commences or continues an action, so the arithmetic between the two sides can be resolved in that one case. If an administrator has filed against you, bring the complaint and your own supporting documents to a lawyer promptly, because the opportunity is tied to that action.